IT'S THE photo that's brought people the world over to tears.
Sully, George H.W. Bush's service dog, is pictured resting mournfully in front of his owner's casket.
The former US president's spokesman Jim McGrath posted the picture of the Labrador with the caption, "Mission complete. #Remembering41".
Mr Bush received Sully in June from America's VetDogs nonprofit organisation.
At the time he tweeted what a joy it was to get him:
A great joy to welcome home the newest member of our family, "Sully," a beautiful -- and beautifully trained -- lab from @AmericasVetDogs. Could not be more grateful, especially for their commitment to our veterans. pic.twitter.com/Fx4ZCZAJT8— George Bush (@GeorgeHWBush) June 25, 2018
The former president had a form of Parkinson's disease, and Sully could open doors, pick up items and summon help.
CNN reports the Labrador will accompany his master one last time, accompanying Mr Bush's casket on a flight to Washington.
Thousands of people have been sharing their emotion over the touching photo.
"It's 12.30am on a school night and I'm crying," wrote one woman.
"This is so precious and heartbreaking at the same time," wrote another.
"I'm sobbing," others said.
Sully has his own Instagram account with more than 73,000 followers.
He will return to America's VetDogs in New York through the holiday season before joining the Water Reed National Military Medical Center's Facility Dog Program.
"Our thoughts and prayers are with the entire Bush family during this difficult time," said John Miller, head of America's VetDogs.
"It was truly an honour to have provided service dog Sully to be by the president's side for the past several months."
Mr Bush will be honoured in several public and private events in Houston and Washington before his burial Thursday in Texas.